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    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>  
    //     //向上取整
    //     console.log(Math.ceil(1.2));
    //     console.log(Math.ceil(1.5));
    //     console.log(Math.ceil(1.8));
    //     console.log(Math.ceil(-1.2));
    //     console.log(Math.ceil(-1.5));
    //     console.log(Math.ceil(-1.8));
    //    //向下取整
    //     console.log(Math.floor(1.2));
    //     console.log(Math.floor(1.5));
    //     console.log(Math.floor(1.8));
    //     console.log(Math.floor(-1.2));
    //     console.log(Math.floor(-1.5));
    //     console.log(Math.floor(-1.8));

    //     //四舍五入
    //     console.log(Math.round(1.2));
    //     console.log(Math.round(1.5));
    //     console.log(Math.round(1.8));
    //     console.log(Math.round(-1.2));
    //     console.log(Math.round(-1.5));
    //     console.log(Math.round(-1.8));

    //向上取整
    console.log(Math.ceil(1.2));
    console.log(Math.ceil(-1.8));
    //向下取整
    console.log(Math.floor(1.8));
    console.log(Math.floor(-1.2));
</script>

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<body>
    
</body>
</html>